Digital-to-analog converters (DACs) are useful for many applications. For example, a compact disc (CD) player retrieves information stored digitally on the CD and a DAC converts the information to an analog signal. The analog output of the DAC is then provided to a speaker. For a CD player, it is necessary to retrieve stereo information, having a left channel and a right channel. Commercial integrated circuits for CD players thus must provide a data interface for the information received from the CD, separate the information corresponding to the left and right channels, and process the left and right channel information in two separate DACs. Several DAC architectures are known, including switched-capacitor, R2R, and sigma-delta.
Several problems arise in these integrated circuits. Each sample on a CD has a certain size, typically sixteen bits. The integrated circuit receives the data serially but processes the data in corresponding multi-bit data words. DACs commonly come in different word sizes for different applications, but as technology expands, word lengths tend to increase. Another problem is that when the system is powered up or down, the DAC may go into an indeterminate state in which it can provide an output signal corresponding to large analog signals. When the DAC provides these large analog signals to a speaker, the result is undesirable audio pops. One method to eliminate the audio pops is to put relays at the output of the DAC to disable the output when the system is being powered up or down. However, these relays increase product cost because they are expensive and consume a significant amount of board space. A further problem is that in some circumstances board space is very limited, and extra pins on the integrated circuit are especially undesirable. A minimization of the number of pins would reduce the amount of board space. Each of these problems limits the efficacy with which integrated circuits for digital-to-analog applications perform.